The idea of this feat is to enable large numbers of weak creatures to be more effective against powerful individual creatures. It's inspired by a comment on an old thread about an improved mob template.
Volley Shot [General] Prerequisites
Point Blank Shot.
You may use the Aid Another action to help a friend within one range increment of your weapon. You may fire a shot against an enemy within one range increment, but make the attack roll against AC 10 as usual. This special attack otherwise works as stated.
You may only use Aid Another in melee.
A fighter may select Volley Shot as one of his fighter bonus feats.
You may attempt to conceal which of you was aided by making a special Hide check as a free action with a -10 penalty (which includes the -20 penalty for hiding in combat, and a special +10 bonus for concealing use of tactics). Neither you nor your friend need concealment or cover for this special Hide check, although either concealment or cover (or both) provide a +4 bonus to this check. Your friend's Hide check is used as the DC required for a Spot check to determine which of you is being aided; your check result is used for Aiding Another on your friend's skill check.
I'm pretty sure the wording (most of which was adapted from Aid Another) still needs some cleaning up and polishing.
Here's an example of the feat in action. Unfortunately, my encounter-building skills are not really on par with my homebrewing skills, so please excuse the oddities and politely correct the mistakes; the main flaw this feat leaves behind (lack of damage per shot) is here corrected for with consumables.
encounter, CR 16 (26792gp gear) — 8 volley groups, each with the following:
1 archer with 12 +1 collision arrows (1920gp), attacking with at least +24 aid another for a total of +31/+31 ranged (1d6+6)
13 archers with normal arrows, volleying at 95% aid another rate
strategy is to attack from some sort of cover or concealment, preferably trees, cliffs, or cavern outcroppings, with goblins scattered 5-15' apart to make it more difficult either to pinpoint which to kill or to kill them all at once; the buffers, as implied, aren't terribly useful in combat, but that doesn't matter
archer, CR 2
NE Goblin Fighter 2 Size/Type: Small Humanoid (Goblinoid) Hit Dice: 3d10+6 (22 hp) Initiative: +5 Speed: 30 ft. (6 squares) Armor Class: 19 (+1 size, +5 Dex, +3 studded leather armor), touch 16, flat-footed 14 Base Attack/Grapple: +2/-2 Attack: Longbow +9 ranged (1d6+6) Full Attack: Longbow +7/+7 ranged (1d6+6) Space/Reach: 5 ft./5 ft. Special Attacks: — Special Qualities: Darkvision 60 ft. Saves: Fort +5, Ref +6, Will +2 Abilities: Str 10, Dex 21 (including +4 enh from Cat's Grace), Con 14, Int 10, Wis 13, Cha 6 Skills: Hide +16, Listen +4, Move Silently +13, Ride +9, Spot +1 Feats: Point Blank Shot, Rapid Shot, Volley Shot
NE Goblin Druid 4 Size/Type: Small Humanoid (Goblinoid) Hit Dice: 3d8+6 (19 hp) Initiative: +2 Speed: 30 ft. (6 squares) Armor Class: 17 (+1 size, +2 Dex, +4 hide armor), touch 13, flat-footed 15 Base Attack/Grapple: +3/-1 Attack: Sling +4 ranged (1d3-1) or quarterstaff +1 melee (1d4-1) Full Attack: Sling +4 ranged (1d3-1) or quarterstaff +1 melee (1d4-1) Space/Reach: 5 ft./5 ft. Special Attacks: — Special Qualities: Darkvision 60 ft. Saves: Fort +5, Ref +3, Will +5 Abilities: Str 8, Dex 15, Con 14, Int 12, Wis 15, Cha 6 Skills: Concentration +8, Handle Animal +2, Hide +13, Knowledge (nature) +4, Listen +8, Move Silently +13, Spellcraft +7, Spot +8, Survival +5 Feats: Augment Summoning, Spell Focus (Conjuration)
0: Cure Minor Wounds (x4)
1: Pass Without Trace (x4)
2: Cat's Grace, Flaming Sphere, Barkskin
Casts cat's grace on the primary archer in group
Usually converts flaming sphere and barkskin into SNA II: 1d3 wolves, which are strewn about the battlefield
Assumed to have enough time to finish these castings but still have them running
hide armor (15gp)
mastermind, CR 10
NE Goblin Wizard 10
arranges for tactics, uses divinations for strategy; encountered later